class EventEmitter{
    constructor() {
      // {'click':[fn1,fn2], 'change':[fn]}
      this.subs = Object.create(null);
    }

    // 注册事件
    $on(eventType, handler) {
      this.subs[eventType] = this.subs[eventType] || [];
      this.subs[eventType].push(handler);
    }
    
    // 触发事件
    $emit(eventType) {
      if(this.subs[eventType]){
        this.subs[eventType].forEach(handler => {
          handler();
        });
      }
    }
  }

export default EventEmitter